[light] Shrink LightState by 12 bytes per light (#19711)

tests/components/light/test_light_state.cpp

@@ -0,0 +1,68 @@
+#include <gtest/gtest.h>
+
+#include "esphome/components/light/light_effect.h"
+#include "esphome/components/light/light_output.h"
+#include "esphome/components/light/light_state.h"
+
+namespace esphome::light::testing {
+
+namespace {
+
+class BrightnessOutput : public LightOutput {
+ public:
+  LightTraits get_traits() override {
+    LightTraits traits;
+    traits.set_supported_color_modes({ColorMode::BRIGHTNESS});
+    return traits;
+  }
+  void write_state(LightState *state) override {}
+};
+
+class NoopEffect : public LightEffect {
+ public:
+  using LightEffect::LightEffect;
+  void apply() override {}
+};
+
+// start_effect_() is where the uint32_t index is narrowed to the stored uint16_t.
+class TestableLightState : public LightState {
+ public:
+  using LightState::LightState;
+  using LightState::start_effect_;
+};
+
+}  // namespace
+
+// add_effects() is public, so an external component can exceed the codegen cap on effect count;
+// an index the uint16_t can't hold must be ignored rather than wrap onto another effect.
+TEST(LightStateEffect, IndexAboveUint16IsIgnoredAndKeepsTheActiveEffect) {
+  BrightnessOutput output;
+  TestableLightState state(&output);
+  NoopEffect effect("Noop");
+  state.add_effects({&effect});
+
+  state.start_effect_(1);
+  ASSERT_EQ(state.get_current_effect_index(), 1u);
+
+  state.start_effect_(0x10000u);  // unchecked narrowing wraps this to 0, which stops the effect
+  EXPECT_EQ(state.get_current_effect_index(), 1u);
+}
+
+// get_gamma_correct() reads the gamma codegen stores after the lookup table, rounded to two decimals.
+TEST(LightStateGamma, ReadsTheGammaStoredWithTheTable) {
+  static constexpr GammaTable TABLE{{}, 280};
+  BrightnessOutput output;
+  LightState state(&output);
+  state.set_gamma_table(&TABLE);
+  EXPECT_FLOAT_EQ(state.get_gamma_correct(), 2.8f);
+  EXPECT_EQ(state.get_gamma_table(), TABLE.lut);
+}
+
+TEST(LightStateGamma, IsZeroWithoutATable) {
+  BrightnessOutput output;
+  LightState state(&output);
+  EXPECT_FLOAT_EQ(state.get_gamma_correct(), 0.0f);
+  EXPECT_EQ(state.get_gamma_table(), nullptr);
+}
+
+}  // namespace esphome::light::testing